北京市房地产类建设项目下凹式绿地的雨水拦蓄能力及挖深研究

Storage Capacity and Digging Depth for Rainwater Collection on Low Elevation Green Land in Projects of Real Estates in Beijing City

下凹式绿地是解决由城市大量房地产建设引发的排洪压力和降水径流流失等问题的一种有效措施。通过设计暴雨产汇流计算,分析了北京市不同下凹深度绿地的雨洪拦蓄能力。针对北京市房地产类项目绿地率的一般要求,当下凹式绿地率为20%以上,下凹深度为15cm时,对于设计重现期为2a的降雨,拦蓄率可达80%以上;下凹深度20cm时,对于设计重现期为5a的降雨,拦蓄率可达80%以上。从土方挖填平衡的角度提出了下凹式绿地施工挖深的计算方法。结果表明,北京市房地产类项目下凹式绿地设计深度为15～20cm,施工挖深约为6～15cm较为合理。

Low elevation green land is an effective measure to relief city flood discharge pressure and to reduce runoff losses caused by the establishment of a large amount of real estates. By calculation of runoff yield and flow concentration, the rainwater storage capacity of different green lands with various depths in Beijing City was analyzed. Approximately 80% of the rain with 2-year re-occurrence probability could be sequestrated if the green land ratio was higher than 20% with concave depth of 15 cm as specified by the requirements real estate development in Beijing City. With a concave depth of 20 cm, the sequestration rate could be still higher than 80% for the rains with 5-year re-occurrence probability. Based on the earthwork balance, the calculation method for digging depth of low elevation green land was proposed. According to the calculation and analysis, the design depth should range between 15-20 cm with digging depth of 6-15 cm for low elevation green lands.